Certain types of energy delivery devices are capable of non-ablatively and non-invasively treating a patient's tissue with electromagnetic energy. These energy delivery devices, which emit electromagnetic energy in different regions of the electromagnetic spectrum for tissue treatment, are extensively used to treat a multitude of diverse skin conditions. Among other uses, non-invasive energy delivery devices may be used to tighten loose skin so that a patient appears younger, to remove skin spots or hair, or to kill bacteria.
One variety of these energy delivery devices emit high frequency electromagnetic energy in the radio-frequency (RF) band of the electromagnetic spectrum. The high frequency energy may be used to treat skin tissue non-ablatively and non-invasively by passing high frequency energy through a surface of the skin, while actively cooling the skin to prevent damage to the skin's epidermal layer closer to the skin surface. The high frequency energy heats tissue beneath the epidermis to a temperature sufficient to denature collagen, which causes the collagen to contract and shrink and, thereby, tighten the tissue. Treatment with high frequency energy also causes a mild inflammation. The inflammatory response of the tissue causes new collagen to be generated over time (between three days and six months following treatment), which results in further tissue contraction.
Typically, energy delivery devices include a treatment tip that is placed in contact with, or proximate to, the patient's skin surface and that emits electromagnetic energy that penetrates through the skin surface and into the tissue beneath the skin surface. The non-patient side of the energy delivery device, such as an electrode for high frequency energy, in the treatment tip may be sprayed with a coolant or cryogen spray under feedback control of temperature sensors for cooling tissue at shallow depths beneath the skin surface. A controller triggers the coolant spray based upon an evaluation of the temperature readings from temperature sensors in the treatment tip.
The cryogen spray may be used to pre-cool superficial tissue before delivering the electromagnetic energy. When the electromagnetic energy is delivered, the superficial tissue that has been cooled is protected from thermal effects. The target tissue that has not been cooled or that has received nominal cooling will warm up to therapeutic temperatures resulting in the desired therapeutic effect. The amount or duration of pre-cooling can be used to select the depth of the protected zone of untreated superficial tissue. After the delivery of electromagnetic energy has concluded, the cryogen spray may also be employed to prevent or reduce heat originating from treated tissue from conducting upward and heating the more superficial tissue that was cooled before treatment with the electromagnetic energy.
Although conventional methods apparatus and for delivering cryogen sprays have proved adequate for their intended purpose, what is needed are improved methods and apparatus for cooling superficial tissue in conjunction with non-ablative and non-invasive treatment of deeper regions of tissue beneath the skin surface with amounts of electromagnetic energy.